`type` regression if textarea has no value before typing

• @testing-library/user-event version:
• Testing Framework and version: 11.4.2
• DOM Environment: jest@26.0.1 @testing-library/jest-dom@5.9.0 @testing-library/react@10.2.1

Relevant code or config

test(" empty textarea", async () => {
  render(<textarea data-testid="textbox" />);

  await userEvent.type(screen.getByTestId("textbox"), "1234");
  expect(screen.getByRole("textbox")).toHaveValue("1234");
});

What you did:

Updated from 11.2.1 to 11.4.2

What happened:

library code types incorrectly if the textarea has no value when it start typing

Reproduction repository: https://codesandbox.io/s/user-event-type-to-add-text-issue-exgpf?file=/src/__tests__/App.test.js

Problem description:

It seems like the “type” event returns to the beginning of the line after it has typed the first letter, after that it returns to normal resulting in the first letter always being at the end of the word/sentence

[marcosvega91]

The problem here is that before typing selectionStart and selectionEnd are undefined. I think that can be a problem of jsdom instead.

[ph-fritsche]

@dave-cabbage The reproduction example of this issue works as expected with up-to-date dependencies: https://codesandbox.io/s/user-event-type-to-add-text-issue-forked-dezvq?file=/src/__tests__/App.test.js

Are you by chance using an old version of jsdom?

If your problem does not resolve by updating the dependencies on your project, please file a new issue with a reproduction example like above. 😃